\documentclass{article}[a4paper]
\date{\today}

\usepackage[ngerman]{babel}
\usepackage[T1]{fontenc}

\usepackage{a4wide}
\usepackage{mathtools}
\usepackage{amsthm}
\usepackage{amssymb}
\usepackage{amsmath}
\usepackage{amsfonts}
\usepackage{hyphenat}
\usepackage{tikz}
\usepackage{graphicx}
\usepackage{xcolor}
\usepackage{color}

\usepackage{listings}
\usepackage{minted}

%%% define own enumeration styles
\usepackage{enumerate}

%%% cleaner newline indentation
\usepackage[parfill]{parskip}

%%% break page on new section
\usepackage{titlesec}
\newcommand{\sectionbreak}{\clearpage}

%%% remove page numbers (fancyhdr provides its own)
\usepackage{nopageno}

%%% fancy headers and footers
\usepackage{fancyhdr}
\pagestyle{headings}

%%% theorem-style environments
\usepackage{proof}
\usepackage[skins]{tcolorbox}

% definition
\theoremstyle{definition}
\newtheorem{definition}{Definition}[section]
\tcolorboxenvironment{definition}{blanker, before skip=10pt,after skip=10pt}

% example
\theoremstyle{definition}
\newtheorem{example}{Beispiel}[section]
\tcolorboxenvironment{example}{blanker, before skip=10pt,after skip=10pt}

% theorem
\newtheorem{theorem}{Satz}[section]
\tcolorboxenvironment{theorem}{blanker, before skip=10pt,after skip=10pt}

% algorithm
\theoremstyle{definition}
\newtheorem{algo}{Algorithmus}[section]
\tcolorboxenvironment{algo}{blanker, before skip=10pt,after skip=10pt}

% remark
\theoremstyle{definition}
\newtheorem*{remark}{Bemerkung}
\tcolorboxenvironment{remark}{blanker, before skip=10pt,after skip=10pt}